‘Myself and two other runners – they were both doctors – ran over to him, flipped him over and started doing chest compressions.’

Despite paramedics arriving to continue resuscitation efforts, the man was taken to Queen’s Medical Centre where he was pronounced dead at around 10.30am.

The run took place at Forest Recreation Ground, Nottingham – a weekly event, which provides time trials for all runners.

Weekly Park Runs are held around the country, offering a free timed run for people and a way for runners to socialise.

Mr Herbert, a chemistry teacher who lives in Nottingham, said the man who died had looked ‘the picture of health, apart from the fact he was in a really bad state’.

Nottinghamshire Police said the death is not being treated as suspicious and a report will be submitted to the coroner.

In a statement, Forest Rec Park Run said: ‘You may be aware a parkrunner collapsed during the run on March 18. Several parkrunners attempted to resuscitate him, as did an ambulance crew. However we are very sorry to have to report that all efforts were unsuccessful.

‘Our thoughts and deepest sympathies are with friends and family for their loss.’